The invention relates to a reclining device having a body support or mattress support as the reclining surface with several movable parts which can adjust the shape of the curvature of the spinal column. The lumbar vertebrae are thought of here specifically, but also other regions of the spinal column. In the case of such a reclining device it can be, for example, a slatted frame for a bed, a recliner, a mattress, a waterbed, equipment for spinal column therapy or an armchair which can be converted into a recliner.
With many bedframes the head section, the back section and/or the foot section is adjustable so that a more comfortable position can be adopted.
The previous assumption was that a hollow back (lordosis) is positive, because it supports the natural curvature of the spinal column. In the case of chairs and seats one therefore usually finds a lumbar pad. For the same reason one can find recommendations, for example, to push a cushion behind the back. A flat or rounded back (kyphosis), on the other hand, was to be avoided according to many recommendations, because great stress was placed on the intervertebral disk. It was assumed that this increased pressure accompanied by a wedge-shaped aperture angle pressed the nucleus of the vertebral disks (nucleus pulposus) to the rear and thus caused problems. These findings were based primarily on in vivo intradiscal studies which were carried out in the sixties. These measurements showed at the time that the stress when sitting was 40% greater than when standing. Since a lumbar lordotic position is assumed when standing, this position was also to be assumed when sitting to reduce the stress on the spinal column. Previous measurements when sitting showed that the stress here can be reduced if lordosis was supported.
However, the inventor has determined with a direct, in vivo measurement of intervertebral disk pressure that the above findings cannot be substantiated. Sitting, according to his new findings, is no more stressful than standing, thus confirming earlier published results which are based on indirect measuring methods. Pressure in the intervertebral disk in the previously maligned, casual sitting position, i.e. when sitting with a rounded back, can be reduced to one half. (Wilke, H. J., Neef, P., Caimi, M., Hoogland, T., Claes, L. E., New in vivo measurements of pressures in the intervertebral disc in daily life. Spine 1999, Apr 15; 24 (8): 755-62). This maligned, casual, but comfortable sitting position with the back slightly rounded creates significantly less stress on the intervertebral disk than the previously recommended upright sitting position with lordosis, i.e. with lumbar lordosis. These contradictions vis-a-vis the earlier results can be attributed to the different measuring technique.
Through the studies conducted by the inventor it has been shown that a changing compressive load in the intervertebral disk is desirable because the intervertebral disk can be nourished thanks to its ″sponge principle (Wilke, H-J, Claes L. E., (eds.) (1998) The traumatic and degenerative intervertebral disk, Springer Verlag, Heidelberg, ISBN 3-540-65108-X). With the knowledge of these facts, the object of the invention is to create a reclining device of the type named at the beginning, with which it is possible alternately to impose a load on and remove a load from the human spine and other joints.
This object is achieved by means of a reclining device in accordance with claim 1 as well as a method in accordance with claim 13. Advantageous further forms of the inventive reclining device and of the inventive method are given in the specific dependent claims.